Ok, I’m getting the whole picture now. So sound has never come out of this unit since you bought the car? You might be able to follow the audio wires to where the amp was or is installed. It depends on how they ran the wires though. Might be tough to do. Aftermarket amps – especially the high powered ones – are often installed in the trunk area. Mabye take everything out of the truck, even look in the spare tire area, maybe you’ll find it, or see where some holes have been drilled.